A biofilm is a matrix that is aqueous to more than 95%, gelatinous and secreted by bacteria in water in order to foster their proliferation.
It has been observed that the formation of biofilm is related especially to the following four parameters:                the ideal temperature for the biofilm to develop, between 15 to 45° C.;        stagnation or motion in the liquid;        receptivity of the support, i.e. especially its surface state, the presence of scaling or corrosion, etc;        the presence of favorable nutrients (especially organic residues).        
A major growth of biofilm is often noted in condensate recovery containers. This biofilm can also grow in gravity pipes designed to convey condensates into the container, especially when the section and the slope are too small. This causes the clogging of the pipes which can be filled with biofilm entirely or to a large extent.
In the same way, in a container, the presence of biofilm limits the volume available for the condensates and can disturb or even prevent the efficient working of a removal pump.
Besides, naturally, for hygiene and health, it is not desirable to allow such bacteria-friendly biofilms to develop. For example, biofilm can often be found in the recovery containers of removal pumps associated with refrigerated display cases, for example in supermarkets.
In order to delay the formation of biofilm in containers, there are known ways of placing antibacterial agents in these containers. Such methods are described for example in the documents EP 1 840 475, US 2007 119 503 and EP 2 085 711. In general, the efficacy of these methods against the appearance of biofilm is only temporary. Besides, these methods are costly because they require the regular adding of chemical products into the containers. Because of this, they are also not very environment-friendly.
Other documents such as the document EP 1 835 236 mention the implementation of biocide surface treatment on the walls of a container to prevent biofilm from forming on them. In the same way, the efficacy of such treatment is only temporary, since the surfaces ultimately get colonized by the biofilm all the same.
Certain metals, such as copper or silver, are often considered to be toxic for bacteria. However, their efficacy is still a matter of dispute. Thus, the Internet site www.girpi.fr indicates that “all materials can be colonized by microorganisms, including copper which is nevertheless wrongly considered to be bactericidal”. Besides, it has indeed been observed that the use of copper pipes does not prevent the formation of biofilm.
Certain removal pump manufacturers also integrate copper elements that are unsuccessful in preventing the formation of biofilm: it is indeed necessary to clean the filters periodically and use a biocide product that has to be regularly replaced.